Turbine control mechanism



Sept. 6, 1932. o. B RYANT TURBINE C ONTROL MECHANISM Filed Aug. 50, 1930INVENTOR Ozro IV. Bryant ATTORNEY ESE All

' opening.

Patented Sept. 6, 1932 ,uuiren STATES PATENT: oF- ic ozrto N. BRYANT, orMOORES, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE nLEc TRIO a MANUFACTURINGCOMPANY, A CORPORATION or PENNSYLVANIA TURBINE CONTROL MECHANISMApplication filed August 30, 1930. Serial No, 473,929.

My invention relates to a control mechanlsm for a prlme mover, moreparticularly to a control mechanism for a multistage elas- I tie fluidprime mover having openings at two or more intermediate-pressure stagesfor extracting partially expanded motive fluid from the prime mover orfor admitting motive fluid thereto, and it has for its object to providean improved construction of such mechanism;

A specific object is to provide an improved control mechanism operativeto regulate the flow at each extraction opening in responsetothepressure of the extracted motive fluid, and to compensate theadmission of motive fluid to the prime mover in accordance with theamount of motive fluid extracted at each of said openings.

In accordance with the present invention, I provide a control mechanismncludlng means associated with each extraction opening for providing aregulating fluid pressure which varies with the extraction pressure andwhich regulates the flowof fluid at the Another variable fluid pressureresponsive to the regulating fluid pressures compensates the admissionof motive fluid to the prime mover.

These and other objects are effected by my invention, as will beapparent from the following description and claims taken in connectionwith the accompanying drawing, forming a part of this application, inwhich:

The single figure is a diagrammatic representation of the controlmechanism appliedto an elastic fluid turbine.

Referring now to the drawing more in detail, I show a turbine having anadmission valve 11, and openings 12 and 13-communieating withintermediate-pressure stages in the turbine indicated at 14 and 15,respectively. The openings 12 and 13 communicate with conduits 12' and13, respectively, and partially expanded motive fluid may be ex tractedfrom the intermediate pressure stages through the respective openingsand conduits. Diaphragms 16 and 17 are interposed.

between the pressure stages 14 and and r the succeeding turbine stages,and conduits 18 and 19 provide lay-passes around the diaphragms, throughwhich the motive fluid not extracted maybe conveyed to continue itsexpansion in'a lower pressure stage or stages of the turbine;

Valves 21 and 22 are provided in the by pass conduits l8'and'l9,respectively, to reg- I ulate the flow of motive fluid therethrough; Bycontrolling the amount of fluid held back from the lower pressurestages, these valves regulate the flow through the openings 12 and 13and maintain the pressures at the extraction stages. It will be apparentto those skilledin the art that any other'construc-- tion whichregulates thedistribution of fluid between the extraction opening andthe succeeding turbine stages may be used as the equivalent of theby-pass valve.

The admission valve 11 and the bypass valves 21 and 22 are controlled bygovernors- 23, 24 and 25, respectively, which may be and are shown assimilar in construction. Each governor includes a'piston 26, whichoperates in a cylinder 27 and is connected to the associated valve inanyv suitable manner, as through a fulcrum lever 84:. Fluid pressurepreferably in the piston 26, through which a restricted flow offluid'under pressure provided by the impeller 28 is admitted to theupper end of the cylinder 27 above the piston 26.

A back pressure is imposed on the fluid flowing through the orifice bycontrolling its escape from the upper end of the cylinder, and thispressure biases the piston 26 in cooperation with the springs 32 and inopposition to the variable fluid pressure beneath the piston; The backpressure in the governor 24 is controlled in responseto pressure at theextraction opening 12, that in the governor inresponse to-pressure atthe opening 13, and that in the governor 23 in response to both of saidpressures. The mechanism for accomplishing this function will now bedescribed.

The upper end of the cylinder of the governor 24 communicates, through aconduit 35, with a pressure relief valve 36 which controls the pressurein the upper end of said cylinder. The pressure reli f valve is biasedto closed position by a compression spring 37 interposed between thevalve and a spring abutment 38. The latter is connected to a lever 39fulcrumed at 41.

A diaphragm 42 is subjected to the pressure of the fluid extractedthrough the opening 12 and the conduit 12, communicating thereto througha conduit 43. The diaphragm transmits the force of the fluid pressurethereon to the lever 39 in opposition to the force of the spring 37. Agroup of weights 44 further bias the lever 39 against the force of thefluid pressure on the diaphragm 42.

The upper end of the cylinder of the governor 25 communicates, through aconduit 45, with a pressure relief valve 46, which controls the backpressure in said governor. The valve 46 is likewise biased to closedposition by a compression spring 47 interposed between the valve and aspring-holding member 48. The latter is connected to a lever 4 fulcrumedat 51.

The diaphragm 52 is subjected to the pressure of the fluid flowingthrough the opening .13 and the conduit 13, communicated thereto througha conduit 53. The force of the fluid pressure on the diaphragm 52 istransmitted to the lever 49 in opposition to the force of the spring 47.A. group of weights 54 biases the lever 49 in opposition to the force ofthe fluid pressure.

The back pressure in the governor 23 iscontrolled by a device which maybe termed a compensator, and which is indicated by the numeral 55. Thelatter includes a pressure relief valve 56 which communicates, through aconduit 57, with the upper end of the cylinder of the governor 23 andcontrols the back pressure therein. The pressure relief valve is biasedto closed position by a spring 58, the bias being transmitted to thevalve through a stem 59 abutting the valve and having a collar 61contacting with the spring 58. The stem 59 is formed at its upper endwith a downwardly-facing knife edge 62.

The control device further includes levers 63 and 64, abutting againstknife edge fulcrums 65 and 66, respectively. The knife edges 65 and 66are carried by a stationary plate 67. The latter is formed withlongitudinal slots 68, and the knife edges 65 and 66 are secured to theplate by screws 69 which extend through the slots 68.

The levers 63 and 64, at their adjacent ends, engage the knife edge 62.Intermediate their ends, the levers 63 and 64 are engaged bypressure-responsive elements 71 and 72, subjected to the back pressuresprovided by the pressure relief valves 36 and 46, respectively,communicated through extensions of the conduits 35 and 45. g

The operation of the above-described mechanism is as follows:

The admission valve 11 and the by-pass valves 21 and 22 all move inresponse to changes in speed of the turbine by reason of the impellerpressure imposed on the underside of each governor piston 26. Uponincrease in speed, the impeller pressure increases, moving the pistons26 upwardly against the spring 32 to move the valves in closingdirection by amounts in accordance with the increase in impellerpressure. The flow of fluid is thus decreased throughout the length ofthe turbine. The pressure at each extraction opening, however, remainssubstantially the same.

Upon decrease in speed and decrease in fluid pressure, the springs 32move the pistons 26 to increase the valve openings.

The desired pressures of the fluid at the extraction stages 14 and 15are maintained in the following manner:

Assume that the demand for motive fluid from the pressure stage 14increases, resulting in a decreased pressure in the conduit 12. Thedecreased pressure is communicated to the diaphragm 42, decreasing thecompression of the spring 37. The closing force on the pressure reliefvalve 36 is decreased, and

the latter decreases the back pressure in the governor 24.

The impeller pressure below the piston 26 in the governor nowpreponderates and moves the piston upwardly to decrease the opening ofthe by-pass valve 21. More fluid is thus held back from the lowerpressure stages to supply the demand for extracted fluid and to maintainthe pressure thereof.

Upon decrease in demand and increase in extraction pressure, the reverseoperation takes place. The compression of the spring 37 is increased,and the valve 36 provides an increased back pressure in the governor 24.The piston thereof thereupon moves the bypass valve in opening directionto pass the excess motive fluid to the lower pressure stages of theturbine.

Changes in extraction pressure in the conduit 13 are communicated in asimilar manner to the diaphragm 52, moving the lever 49 to vary thecompression of the spring 47 and the pressure provided by the reliefvalve 46 in the governor 25. The governor 25 controls the by-pass valve22 to hold back sufflcient motive fluid for supplying the requiredamount of extracted fluid to the conduit 13 and for maintaining thepressure thereof.

The changes in demand for extracted fluid at either opening affect theamount of work done by the fluid in carrying the turbine load, since, aswill be apparent, the fluid extracted does not complete its expansion inthe lower stage or stages. It is, therefore, necessary to compensate theadmission valve for the amount of fluid extracted to the openings and,in accordance with the present invention, this is accomplished by thecompensator 55. As the demand for fluid from the pressure stage 14decreases, for example, the pressure increases and the pressure reliefvalve 36 increases the back pressure in the governor 24, effectingopening movement of the bypass valve 21. The increased back pressure isconveyed through the conduit 35 to the pressure-responsive element 71,which transmits an increased upward force to the lever 63.

The latter, by reason of its engagement with the knife edge 62,transmits the increased upward bias to the stem 59 in opposition to theforce of the spring 58. The resultant or net closing force on thepressure relief valve. 56 is thereby decreased, providing a decreasedback pressure in the governor 23. The impeller pressure in the governor23 preponderates and moves the piston 26 in valve closing direction fordecreasing the admission of motive fluid to the turbine. The decrease inload thus carried by the highpressure end of the turbine compensates forthe increase of load carried by the lower pressure stages upon openingmovement of the by-pass valve 21.

Upon increase in demand for extracted fluid at the opening 12, thereverse operation takes place, as will be apparent.

Upon change in demand and pressure at the opening 13, the correspondingchange in back pressure in the conduit 45 acts upon thepressure-responsive element 72 to vary the upward bias transmitted bythe lever 64 to the stem 59. The closing force on the pressure reliefvalve 56 is varied in'the same manner to vary the back pressure in thegovernor 23, which effects the required compensation of the admission tothe turbine.

In order to provide the desired increment of compensating movement ofthe valve 11 upon a given increment of movement of either of the by-passvalves, an adjustment is provided in the compensator. Such adjustmentmay be eflected by moving the corresponding knife edge 65 or 66 to varythe lever arm ratios of the corresponding lever 63 or 64.

It will be apparent that the pressure within the region enclosed by anextraction pressure stage and the opening and extraction conduitcommunicating therewith is substantially the same, or at least variessimilarly with changes in demand, and that the pressure for controllingthe associated pressure-responsive diaphragm may be taken at any pointwithin that region.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited but is susceptible ofvarious changes and modifications without departing from the spiritthereof, and I desire, therefore, that only such limitations shall beplaced thereupon as are imposed by the prior art or as are specificallyset forth in the appended claims.

What I claim is:

1. The combination with an elastic fluid prime mover having an admissionvalve and extraction or admission openings communicating with twointermediate-pressure stages therein, of a governing system thereforcomprising means associated with each of said pressure stages forproviding a fluid pressure varying in response to the pressure at saidstage and for regulating the flow of fluid at the pressure stage inresponse to said variable fluid pressure, means responsive to both ofsaid variable fluid pressures for providing a third variable fluidpressure, and means responsive to said third variable fluid pressure forregulating said admission valve.

2. The combination defined in claim 1 and further comprising meansproviding a fluid pressure varying as a function of the speed of theprime mover, each of the regulating means being further responsive tothe lastmentioned fluid pressure.

3. The combination with an elastic fluid prime mover having an admissionvalve and extraction or admission openings communicating with twointermediate pressure stages therein, of a governing mechanism thereforcomprising means providing a fluid pres sure varying as a function ofthe speed of the prime mover, a control device associated with eachopening and providing a fluid pressure varying in response to change inpressure at the opening and in the same direction as such change, acompensator providing a fluid pressure varying in response to change ineither of the last-named fluid pressures and in the direction oppositeto such change, means responsive to the first mentioned fluid pressureand to the fluid pressure provided by the compensator for controllingtheadmission valve, and means for controlling the flow at each opening inresponse to the first mentioned fluid pressure and to the fluid pressureprovided by the associated control device.

In testimony whereof, I have hereunto subscribed my name this 29th dayof August,

OZRO N. BRYANT.

